The goals of research described in this application are twofold: to elucidate the mechanisms by which a single ovulatory follicle matures each cycle and to identify the physiological mechanisms by which the primate corpus luteum is regulated during the rhesus monkey menstrual cycle. Experiments presented herein will investigate whether the selected follicle inhibits the maturation of other follicles by suppressing gonadotropin secretion, and if the selected follicle is spared from this inhibition by its acquisition of a rich vasculature which allows it to preferentially receive gonadotropins. In addition, this research will define the dependency of the primate corpus luteum on pituitary gonadotropins during the early, mid, and late luteal phase of the menstrual cycle, identify the nature by which the corpus luteum perceives and responds to pituitary gonadotropins, and elucidates the site of action of estradiol in promoting luteal regression. In addition to providing definitive information regarding the physiological regulation of the primate ovary in vivo, the results obtained from these experiments may further our understanding of pathophysiological disturbances of the human menstrual cycle such as impaired follicle growth, the short luteal phase, and the inadequate luteal phase. Lastly, it is becoming increasingly apparent that pulsatile GnRH treatment will be used extensively in the treatment of certain types of amenorrhea in humans. Studies described in this application will provide important information regarding the maintenance of the corpus luteum in GnRH driven menstrual cycles, and in doing so, may directly guide clinical endocrinologists in the effective treatment of infertility.